If there's too much light and not a place to hide the kuhlis freak out. They like a nice cave to stay in and mostly only come out to eat. They prefer shade but will venture a little distance from the cave if there is a posibility of food.
As for the puffers, they're not terribly sensitive to water conditions. The hardest part about raising them is they only eat live food. I've gotten mine to eat live brine shrimp and black/blood worms. I had a puffer die before I realised that
Another tough thing is introducing new puffers. They seem to enjoy groups but are reluctant to include a new puffer in the group. Sometimes it's hard to get the new guys to eat too.
Both the kuhlis and puffers are great though
Oh yeah, another thing to note. Be careful and make sure you watch for any puffers dying. The puffer that died originaly sank to the bottom and I had a couple other fish try to eat him (red tailed sand loaches). The loaches subsequently died (from what I understand their skin is slightly poisonous). The puffers are very hardy, and nobody seems to bother them when they're alive. I had a couple in with my buenos aires and even when the buenos aires tried to eat them the puffers would attack the buenos aires right back. I moved them because I think the buenos aires were stressin' them out a little.
Also, those puffers are almost adults. They're dwarf puffers and only grow to maybe a little over 1". The larger puffers are either brackish or marine (from what I understand, although it's possible there are larger freshwater species).
Hope that helps!